Electric cars are a pipe dream

Well I have to be WRONG first Billy.

The product you linked to is for propane tanks and Propane is stored at a very low 180 psi

You were talking about CNG tanks that operate at 3,600 psi.

Quite a different materials problem Billy.

Arthur

 

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While you say that, sales remain TINY even with huge subsidies.

Without the subsidies no one would buy them.

 

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No Billy, the interstate transportation system is high pressure, but that ends when it enters a city:

The huge distributution system laid out to suburbia and other end users runs at only a few psi.

http://www.naturalgas.org/naturalgas/distribution.asp

Arthur

 

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Here in CA it's around $23,000 for a Leaf - and they are quite popular. There's still a waiting list.

Out the door cost - $36,000
Federal tax credit - $7500
CA tax credit - $5000

Well, gasoline cars are a lot cheaper. But again they have that fossil fuel problem.

If we didn't use it for anything else and we switched just cars over - about 110 years

If we used it for what we use it for now (heating, power) and cars - about 55 years

If we switched all transportation over to natural gas (i.e. trains, aircraft) - 46 years

And of course all of the above is with estimated, not proven, reserves, so it's a high estimate.

So yes, we could use natural gas to push the problem off to our kids. But I think we've been doing that for long enough, personally. Natural gas is a good option, but it should be one part of our fuel makeup; it is certainly not a long term solution for transportation.

 

Yes, currently only few cars and trucks have NG adsorbed as a liquid on high-surface to volume materials. The first hit the road in Feb 2007 with a rectangular tank operating at 500 psi. In a decade there should be many more on the roads than EVs.

Fact that currently most flat tanks are filled with LPG not LNG is no defense for you telling me: I lacked engineering skill, was suggesting an impractical "unobtainium" flat tank that could not be built, and ridiculing me in many posts.

YOU ARE WRONG. You should apologize, but I know you will not - you never admit error or apologize.

“… Ground corncobs, a plentiful agricultural by-product in Missouri and surrounding Corn Belt states, are the main ingredient in a new technology that may soon power natural-gas-powered vehicles on the country's highways. … The initial goal of ANG {Company licensed by MU} is to utilize the high-surface-area carbon in natural gas tanks for ground transportation vehicles within the next year. …”

From: http://munews.missouri.edu/news-releases/2009/0513-suppes-pfeifer-natural-gas-license.php

PS you could make a flat tank that operates at 3600 psi without the filler and its liquid film but there is no need for it with the MU “corn cob” technology. – I have more carefully analysed one (while working on a potential patent application) and even including the fillets it has 8.5% more volume per unit volume of wall material used. What follows is the first draft, but not finished when I learned the flat tanks are commercially available.

Analysis:
Consider a unit length of a long, round, gas filled cylinder, with ID of “D” and walls “t” thick everywhere. Assume the “safety margin” is in t. Assume its axis is the z-axis of a (X, Y, Z) Cartesian coordinate system with the y-axis vertical. This cylinder is but one of many adjoining parallel cylinders whose axes are all in the ZX plane. Their intersections with the XY plane are illustrated below, but the one centered on the z a-axis has been made bold. Our attention will focus on it initially.

…OOOOOOO … But for reasons soon to be explained, I will illustrate these cross sections with: …CCCCCCC …

I call the “t-thick” semicircle in the XY plane with y > 0 “upper” (or “U”) and that with y < 0 “bottom” (or “B”) and the two, zero height, “t-wide” bands on the x-axis R & L, (for right & left). Thus: the first R band with x > 0 extend between the points (D/2, 0) and ([D/2] + t, 0).

Note that the pressure induced tension in the “t-thick” semicircles, U & B, is strictly vertical where they join the x-axis bands. I.e. all along all of the R & L bands, the tension force is strictly vertical. Thus, IF there were no pressure difference horizontally across it, a vertical flat slab of height H, and t thickness, parallel to the z-axis, could have always existed separating the two semicircles, U & B, but the tension in semicircles U & B would increase. The reason why there is no horizontal pressure force across theses flat, H tall, slabs is that the gas pressure on both sides is the same. (All these “vertically stretched” tubes are interconnected in a manifold at one end and individually closed at the other end.)

The “first vertical slab” R with x > 0 “belongs” to the first tube to the right of the one centered on the z-axis, not to that z-axis tube. Thus each tube, except one at the extreme right of the set of tubes, has only the three sides: B, L & U, not four “belonging” to it. This is the fundamental reason why the set can contain more gas per unit of wall mass; however H must be greater than D for there to be significantly less material used per unit of gas contained. Now I will address some of the other details and show this gain in material use efficiency mathematically.


For example, at the top wall U (and the bottom of wall B), the tension is still exactly horizontal but increased compared to the round tube. Thus the thickness there would need to be T = t(1+H/D), including the constant safety factor, to keep this flat sided tube from splitting horizontally. If the top U and bottom B were flat, instead of semicircles, they would have a tendency to bow outward but if T >> D this short thick “flat bridge” of length (t/2+D+t/2) spanning the gap D wide would not flex much when the walls are made of very stiff material. Note each tube’s bridge is part of a large flat sheet and only conceptually considered to be (D +t) wide (and T thick) for the analysis of one tube separately.

For a numerical example, taking pi as 3.14, let H = 3.14D, then the flat tops of U & B are “bridges” of thickness 4.14t spanning a gap of only D. If D = 1cm and t = 0.1cm, then the flat bar or bridge is 0.414 cm thick and only 1.0 cm long. Such a thick, short, bar would not bend much as the pressure is increased. It would probably be ripped off the vertical slabs, which are in this numerical case only 0.1 thick before the bending significantly as the failure mode. These t-thick divisions between the adjoining tubes are the “tension webs” holding the large top and bottom sheets (U & B) together.

Proper design of the ends of these tension webs where they join to the large flat sheet (U & B) that closes each of the D wide tubes is a complex computer modeling problem, which models the transformation of the purely vertical stress in the vertical tension web slabs to a purely horizontal stress at the midpoints of horizontal “bridges” U & B spanning the gap D between the tension web divisions between the individual tubes.

To facilitate this 90 degree turn in the stress direction, there would be no square corners where the tension web slabs join the horizontal bridge bars U & B. Instead “fillets” of approximately 0.2 cm radius would exist. Then the gap directly exposed to the gas pressure spanned by the top and bottom bridge bars would be only 0.6 cm when D = 1.0 cm. I assume that a bar with thickness of 0.414 cm spanning a gap of only 0.6 cm surely would have negligible bending. I. e. bending a bar of very stiff material significantly whose thickness is more than 2/3 of its length by uniform pressure applied to one side is not likely to be a problem.

With four “fillets” filling in all corners of each “vertically stretched” tube the volume of a 1cm unit of length along the z-axis times the cross section area of these four 0.2 cm radius “fillets” which is area of a square 0.4 cm on an edge minus the area of a circle 0.4 cm in diameter. Or 0.16 – 3.14 [(0.2)^2] = [0.16 – (3.14x0.04)] = 0.0344 square centimeters. This 0.0344 cc must be added to 1cm length times the rectangular cross section area and subtracted from 1 cm long unit of rectangular contained area’s volume.

The 1cm length of rectangular wall volume is 1 times twice the top bar cross section area + 1Ht or:
2x0.414x(1+0.1) + (3.14x1)x0.1 = 0.828x1.1 + 0.314 = 0.9108 + 0.314 = 1.2248 cc
Thus the total material volume of one centimeter length of the “stretched tube” is 1.2248 + 0.0344 = 1.2592 cc.

One centimeter length of the rectangular tube’s contained volume is: HD = 3.14cc but the 0.0344cc of the fillets is subtracted from this to get the volume of gas contained in each centimeter of the vertically stretched tube’s length. I.e. that 1cm long gas volume is 3.1056 cc.

Thus the gas volume to containing material volume ratio for the stretched tube is 3.1056 / 1.2592 = 2.46633

The ID radius r of a circular tube which also holds 3.1056 cc of gas per centimeter of length is r^2 = 3.1056 / 3.14 = 0.9890440 so r = 0.99451cm or slightly less than D = 1cm. As the wall thickness required is directly proportional to the diameter, the walls are only 0.099451cm thick, also less than t = 0.1cm of the vertically stretched tube. The outer radius of the round walls is 0.99451 +2x0.099451 = 1.193412 whose square is: 1.424232. Thus the difference between the area of ID and OD circles is 3.14(1.4242322 – 0.9890440) =3.14x0.4351882 = 1.3649095 which is significantly greater than the 1.2592 cc of material required by the vertically stretched tube to hold 2.46633 cc of gas per centimeter of length.

SUMMARY: The tube with vertical stretch of 3.14 cm spaced 1cm apart is more efficient in the use of wall material by the factor of 1.3649095 / 1.2592 = 1.0852 or 8.5% more efficient even with the four “fillets” added to the material used and decreasing the gas volume storage capacity; however, the two extreme edges of this set of parallel “stretched tubes” have not been considered. They could be semicircles in cross section with ID of D = 3.14cm. The right most edge tube would have four sides as its vertical wall closes the vertically stretched “C shape” tube adjoining it as illustrated below:

…………….CCCCCCCCCCCCCCCCCCCCCCD

The left most extreme tube, however, like all the others has only three walls previously called B, L, & U but for this tube they are all just one semicircle like a mirror image of the extreme right, “D shaped,” edge tube illustrated above. Because pressure outside of these two “D-shaped tube is atmospheric their walls must 3.14t thick.

Recall t was the wall thickness of a 1 cm diameter circular tube, which included the desired safety factor. The wall of a 3.14cm circular tube would be 3.14 times thicker to have the same safety factor as must these two extreme edge tubes curved semicircular walls. The vertical wall of the “D-shaped” right most tube illustrated above is, however, only t thick, like any other “tension web divider” as it has no pressure difference across it. There are two fillets inside each of the “D-shaped extreme tubes to facilitate the smooth transition of the vertical “tension web” divider stress vertical wall into the outer wall, even thought for these two extreme tube the outer wall is “D-shaped.”

These two D-shaped extreme edge tube if consider to have been joined have the same efficiency as 3.14cm diameter tube, except for the fact there is a 0.1cm bat across the diameter. When there are about 100 parallel tubes in this “flat gas storage” tank the overall efficiency might drop to only 8.4% better than the circular storage tube. 102 of these tubes would be a “flat tank” about 110 + 7= 117cm wide and 2x0.414 + 3.14 = 3.528 cm tall (That is less than 1.4 inches tall - very suitable for mounting on a large truck’s roof as its fuel tank. It could be wider and as long as the truck’s roof and be the roof. It could be thicker for more fuel stored. I.e. D > 3.14 cm)

If D were greater than the assumed 3.14cm then the efficiency relative to any larger circular tube storing the same amount of gas, or any combination of smaller circular tube storing that amount of gas, would be even greater. This is because the efficiency (gas volume to required wall volume) of circular tube tanks does not depend upon their diameter. E.g. if a circular tube’s diameter is made10 times larger, it will hold 100 times more gas but its walls must be 10 times thicker and the circumference is 10 times greater so the wall volume is also 100 times greater with no improvement in the gas volume to wall volume ratio.

Greater material efficiency than a more conventional pressurized gas storage tank is not the main commercial advantage. This “flat tank” could be the roof of an 18 wheeler truck holding CNG fuel for it with much less wind resistance than round tanks sitting on top of the truck or the roof of an intra-city bus, which also need to keep wind resistance as low as possible.

 

You seem to have switched directions here.

First off, you can, of course, build a rectangular tank. Gasoline tanks are rectangular and hold a small amount of pressure. I have a rectangular water tank that holds about 10PSI (head pressure for a 20 foot water column) without bulging too much.

If as you say that rectangular tank can hold 500psi, great. That means it can hold 14% as much as a cylindrical tank, such as the one in the Honda GX. In other words, you could put a rectangular tank in a vehicle, or put a bunch of cylindrical tanks and hold a lot more natural gas.

Your new direction seems to be adsorption. Yes, that's a clever way to store both methane and hydrogen in lower pressure tanks, and has been used for a long time to store hydrogen for fuel cell vehicles. (It's more of an issue with hydrogen since it has such a low volumetric energy density.)

 

No I'm not wrong.

And the issue of pressure was one you accepted right from the beginning:

Post 2143

And then:

And the pressure in the round tanks we were discussing is 3,600 psi

You can't now point to a tank designed for low pressure PROPANE and claim that you were correct about building a tank for HIGH PRESSURE LNG.

Arthur

 

NO!
My posts have all concerned the contained volume to wall volume ratio. I don't think I have ever stated the operating pressure. I have only and consistently (no switch of directions) been showing that with many "three sided" adjoining parallel cylinders (the internal side being long and flat with no pressure across it) the flat tank can have LESS wall material than the conventional single cylinder tank, if both are made of homogenous material. (No fiber tape wrapped around the tank as some of the more expensive ones have.)

i.e. A cheaper design for the cheapest tanks and more than commercially adequate for holding CNG when most of it is a liquid film on a filler in the tank.

 

Obviously not much of one, considering their nationwide sales last month were well less than 1,000 cars. (Ford sells more F-150s every day of the year)

But you know that over 33% subsidy can't last.

Then what?

 

You, not me may have assumed (falsely) that the pressure of the CNG must be 36,000 psi for it to be mostly liquid.

I did not speak of any specific pressure. I spoke of tank volume to wall volume ratios. As it is possible to hold 180 times more CNG than the cheap filler volume placed in the tanks, that is what is important.

 

YES!

Because indeed you have:

And as pointed out in numerous previous posts, the round CNG tanks operate at 3,600 psi

And in Post 2188 you argued with Billvon specifically about your design handling the STANDARD pressure of 3,600 psi.

http://sciforums.com/showpost.php?p=2846535&postcount=2188

Are you really going to argue now that you weren't talking about high pressure CNG tanks Billy?

If you are, then that's just pathetically sad.

Arthur

 

Well, you've said things like "Thus, one can easily make the flat panel NG tank hold more than twice as much NG as a around tank of the same weight!"

Perhaps you meant to say "one can easily make the flat panel NG tank contain more than twice the volume of a round tank." Which might be true depending on form factor constraints. However if your operating pressure is really 500psi then you can only hold 1/4 the amount of CNG, and thus achieve 1/4 the range.

You can also postulate various ways of increasing the capacity of a tank (through adsorbers etc.) They're sort of independent of tank shape.

 

Nonsense! "same pressure" is not any specific pressure. Again it is only you falsely assuming compressed NG tanks must operate at 36,000 psi. True almost all do now as the 180 fold gain in stored gas with ANG filler is a relatively new development - perhaps that most of gas can be liquid film on the ANG filler (at 500 psi) was unknown to you?

 

Now you are just LYING Billy.

Well the Round Tank in the CNG vehicles today, you know the ones we were talking about like the Civic GX, operate at 3,600 psi.

And when you computed the capacity of your tank you did so in liters of CNG and absolutely did not mention the capacity as if it had an ANG filler.

Arthur

 

Read here:
http://munews.missouri.edu/news-releases/2009/0513-suppes-pfeifer-natural-gas-license.php for how to get 180 fold increase at 500 psi compared to CNG only in the gaseous state.

That is true, but for use in a car as floor or especially as roof of an 18 wheeler truck etc, the flat tank has additional advantages vs a round tank (less air resistance) so what is most important is tank volume to wall material volume - i.e. the cost of the tank walls per unit volume of storage capacity. (This assume the ANG filler cost is relative small as it would be when it is corn cobs - currently a disposal problem.)

 

I obviously am not speaking of today's round tanks or pressures. I am speaking of flat tanks and the future. Again I NEVER said the tank operated at 36,000 psi - I said if the flat tank held THE SAME pressure as the round tank it could have less wall material per unit of storage capacity (That does tacitly assume the tanks both tanks are both of the same homogeneous material, not one is steel and the other is aluminum)

As my statement does not state any specific pressure it would apply to 36,000 psi or 50,000 psi. I did have some calculation errors in my earlier, quickly made, posts. See "analysis" part of post 2227 for a specific geometry tank with 8.5% less wall volume per unit storage volume. (As the two side cells are each with the same efficiency as a round tank and end effects were neglected, I lower the efficiency vs round tank at same pressure, same safety factor, to be 1.084

 

Quit LYING.

You plainly said your tanks operated at the SAME pressure of the round tanks in use today Billy.

That's 3,600 psi

And in this post answering Billvon you were clearly talking about handling 3,600 psi pressures:

LOL

Arthur

 

Pretty pathetic Billy.

To be reduced to telling lies so as not to admit you made an error.

AMF

 

No, I said the text in black. You added the part in red. Putting words in my mouth AGAIN! Doing that is lying.

Even the black text does not quote me correctly. I have always and ONLY been saying the round tank and the flat tank operate at the same pressure, never that my tank operates at the 36,000 psi of CNG tanks in common use today.

 

Yep. In fact it specifically mentions that flat tanks don't work at high pressure:

"In addition, by storing the natural gas at lower pressures, the storage tanks can be virtually any shape, rather than having to be cylindrical when using compressed natural gas."

If the ANG was available I'd use a tiny high pressure cylindrical tank instead of a much bigger flat tank. It could be 1/8 the size; you could stash it in the trunk and barely notice it.